Image projection systems are currently used for a wide range of display applications. More often than not, projection systems are used in generally still or motionless environments such as conference rooms.
However, projection systems are subject to accelerations and vibrations in certain applications, such as flight simulators, motion tables, or avionics installations. The motions present in these applications may adversely affect the projected images. For example, image blurring caused by image defocus or simply by moving.
Further, these projection systems may be degraded by mechanical stresses such as shock, large accelerations, and vibration. For example, such stresses may degrade individual components, mountings, and interconnections in the projection systems. Even if these system elements are not degraded by mechanical stresses, the desired spatial relationships between the elements may change, degrading the display output.
One method for reducing the influence of vibrations and other potentially deleterious forces on a projection system is to isolate the system from these sources by, for example, mounting the components using available cushioning supports. However, for projection displays (and other types of relatively complex optical devices) simple cushioning of the components may result in other potentially undesirable effects.
The individual cushion-mounted components may shift relative to each other when subjected to vibration, thereby degrading image quality. For instance, a relative shift of an image source and a projection lens may cause image defocus or other undesirable effect. In addition, differential vibration between components may blur the image through repeated loss of focus or by actual movement of the image on the screen.
If the complete projection system vibrates, the projected beam may vibrate in a way that amplifies the apparent vibration due to the system projection geometry. This amplification factor can be quite large, depending upon the type of motion and the geometry of the system.
Yet another concern with many projection systems is the ability of the individual components comprising the system to resist mechanical stress. Here too, some designs isolate the complete system from mechanical stress. While this might be practical for small systems, it is less workable for larger systems. Furthermore, it also raises the concern that the system “floats” or vibrates relative to the structures holding it. This motion may be acceptable in some scenarios, but often is not acceptable when the projected image must be stable with respect to a specified reference structure.
Another prior art method for protecting projection systems from vibration is to remove the systems from the source of vibration or acceleration completely, as can be found in U.S. Pat. No. 4,343,539. Such a method is significantly limited in applicability, however, as the projection display system is not self-contained and cannot be fully mounted on or within the moving platform such as a vehicle or motion table. Further, the approach does not accommodate arbitrary platform motion as would be necessary for general-purpose use.
The present invention addresses the needs expressed above, as well as other problems associated with existing projection display systems. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.